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  • Thread-safe blocking queue implementation on .NET

    - by Shrike
    Hello. I'm looking for an implementation of thread-safe blocking queue for .NET. By "thread-safe blocking queue" I mean: - thread-safe access to a queue where Dequeue method call blocks a thread untill other thread puts (Enqueue) some value. By the moment I'v found this one: http://www.eggheadcafe.com/articles/20060414.asp (But it's for .NET 1.1). Could someone comment/criticize correctness of this implementation. Or suggest some another one. Thanks in advance.

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  • Minimizing Java Thread Context Switching Overhead

    - by binil
    I have a Java application running on Sun 1.6 32-bit VM/Solaris 10 (x86)/Nahelem 8-core(2 threads per core). A specific usecase in the application is to respond to some external message. In my performance test environment, when I prepare and send the response in the same thread that receives the external input, I get about 50 us advantage than when I hand off the message to a separate thread to send the response. I use a ThreadPoolExecutor with a SynchronousQueue to do the handoff. In your experience what is the acceptable delay between scheduling a task to a thread pool and it getting picked up for execution? What ideas had worked for you in the past to try improve this?

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  • Processes Allocation in .Net

    - by mayap
    I'm writing some program which should perform calculations concurrently according to inputs which reach the system all the time. I'm considering 2 approaches to allocate "calculation" processes: Allocating processes in the system initialization, insert the ids to Processes table, and each time I want to perform calculation, I will check in the table which process is free. The questions: can I be sure that those processes are only for my use and that the operating system doesn't use them? Not allocating processes in advance. Each time when calculation should be done ask the operating system for free process. I need to know the following inputs from a "calculation" process: When calculation is finished and also if it succeeded or failed If a processes has failed I need to assign the calculation to another process Thanks in advance. Any help would be appreciated.

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  • Threading Problems in ActionScript 2.0?

    - by yar
    Is it possible to have concurrency problems (thread competition) in an onEnterFrame method in ActionScript 2.0? I have written this cheesy code as a guard: if (!busy) { // I suspect some threading problems: is that even possible in flash busy = true; movePanels(); busy = false; } but this is no assurance against thread competition. If so, how can I do a basic semaphore/lock? Note: I suspect threading problems in my app, but if they're impossible, I'll check my code differently.

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  • Simple prime number program - Weird issue with threads C#

    - by Para
    Hi! This is my code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; namespace FirePrime { class Program { static bool[] ThreadsFinished; static bool[] nums; static bool AllThreadsFinished() { bool allThreadsFinished = false; foreach (var threadFinished in ThreadsFinished) { allThreadsFinished &= threadFinished; } return allThreadsFinished; } static bool isPrime(int n) { if (n < 2) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } int d = 3; while (d * d <= n) { if (n % d == 0) { return false; } d += 2; } return true; } static void MarkPrimes(int startNumber,int stopNumber,int ThreadNr) { for (int j = startNumber; j < stopNumber; j++) nums[j] = isPrime(j); lock (typeof(Program)) { ThreadsFinished[ThreadNr] = true; } } static void Main(string[] args) { int nrNums = 100; int nrThreads = 10; //var threadStartNums = new List<int>(); ThreadsFinished = new bool[nrThreads]; nums = new bool[nrNums]; //var nums = new List<bool>(); nums[0] = false; nums[1] = false; for(int i=2;i<nrNums;i++) nums[i] = true; int interval = (int)(nrNums / nrThreads); //threadStartNums.Add(2); //int aux = firstStartNum; //int i = 2; //while (aux < interval) //{ // aux = interval*i; // i=i+1; // threadStartNums.Add(aux); //} int startNum = 0; for (int i = 0; i < nrThreads; i++) { var _thread = new System.Threading.Thread(() => MarkPrimes(startNum, Math.Min(startNum + interval, nrNums), i)); startNum = startNum + interval; //set the thread to run in the background _thread.IsBackground = true; //start our thread _thread.Start(); } while (!AllThreadsFinished()) { Thread.Sleep(1); } for (int i = 0; i < nrNums; i++) if(nums[i]) Console.WriteLine(i); } } } This should be a pretty simple program that is supposed to find and output the first nrNums prime numbers using nrThreads threads working in parallel. So, I just split nrNums into nrThreads equal chunks (well, the last one won't be equal; if nrThreads doesn't divide by nrNums, it will also contain the remainder, of course). I start nrThreads threads. They all test each number in their respective chunk and see if it is prime or not; they mark everything out in a bool array that keeps a tab on all the primes. The threads all turn a specific element in another boolean array ThreadsFinished to true when they finish. Now the weird part begins: The threads never all end. If I debug, I find that ThreadNr is not what I assign to it in the loop but another value. I guess this is normal since the threads execute afterwards and the counter (the variable i) is already increased by then but I cannot understand how to make the code be right. Can anyone help? Thank you in advance. P.S.: I know the algorithm is not very efficient; I am aiming at a solution using the sieve of Eratosthenes also with x given threads. But for now I can't even get this one to work and I haven't found any examples of any implementations of that algorithm anywhere in a language that I can understand.

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  • Python Terminated Thread Cannot Restart

    - by Mel Kaye
    Hello, I have a thread that gets executed when some action occurs. Given the logic of the program, the thread cannot possibly be started while another instance of it is still running. Yet when I call it a second time, I get a "RuntimeError: thread already started" error. I added a check to see if it is actually alive using the Thread.is_alive() function, and it is actually dead. What am I doing wrong? I can provide more details as are needed.

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  • boost thread pool

    - by Dtag
    I need a threadpool for my application, and I'd like to rely on standard (C++11 or boost) stuff as much as possible. I realize there is an unofficial(!) boost thread pool class, which basically solves what I need, however I'd rather avoid it because it is not in the boost library itself -- why is it still not in the core library after so many years? In some posts on this page and elsewhere, people suggested using boost::asio to achieve a threadpool like behavior. At first sight, that looked like what I wanted to do, however I found out that all implementations I have seen have no means to join on the currently active tasks, which makes it useless for my application. To perform a join, they send stop signal to all the threads and subsequently join them. However, that completely nullifies the advantage of threadpools in my use case, because that makes new tasks require the creation of a new thread. What I want to do is: ThreadPool pool(4); for (...) { for (int i=0;i<something;i++) pool.pushTask(...); pool.join(); // do something with the results } Can anyone suggest a solution (except for using the existing unofficial thread pool on sourceforge)? Is there anything in C++11 or core boost that can help me here? Thanks a lot

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  • Progressbar behaves strangely

    - by wanderameise
    I just created an application in C# that uses a thread which polls the UART for a receive event. If data is received an event is triggered in my main thread (GUI) and a progress bar is controlled via PerformStep() method (of course, I previously set the Max value accordingly). PerformStep is invoked using the following expression to handle cross threading this.Invoke((Action)delegate{progressBar2.PerformStep();}) When running this application the progressbar never hits its final value. It stops at 80%. When debugging and stopping at the line mentioned above, everything works fine using single steps. I have no idea what is going one! Start read thread on main thread: pThreadWrite = new Thread(new ThreadStart(ReadThread)); pThreadWrite.Start(); Read Thread: private void ReadThread() { while(1) { if (ReceiveEvent) { FlashProgressBar(); } } } Event that is triggered in main thread: private void FlashProgressBar() { this.Invoke((Action)delegate { progressBar2.PerformStep();}); } (It's a simplified representation of my code) It seems as if the internal progress is faster than the visual one.

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  • Does the managed main UI thread stay on the same (unmanaged) Operation System thread?

    - by Daniel Rose
    I am creating a managed WPF UI front-end to a legacy Win32-application. The WPF front-end is the executable; as part of its startup routines I start the legacy app as a DLL in a second thread. Any UI-operation (including CreateWindowsEx, etc.) by the legacy app is invoked back on the main UI-thread. As part of the shutdown process of the app I want to clean up properly. Among other things, I want to call DestroyWindow on all unmanaged windows, so they can properly clean themselves up. Thus, during shutdown I use EnumWindows to try to find all my unmanaged windows. Then I call DestroyWindow one the list I generate. These run on the main UI-thread. After this background knowledge, on to my actual question: In the enumeration procedure of EnumWindows, I have to check if one of the returned top-level windows is one of my unmanaged windows. I do this by calling GetWindowThreadProcessId to get the process id and thread id of the window's creator. I can compare the process id with Process.GetCurrentProcess().Id to check if my app created it. For additional security, I also want to see if my main UI-thread created the window. However, the returned thread id is the OS's ThreadId (which is different than the managed thread id). As explained in this question, the CLR reserves the right to re-schedule the managed thread to different OS threads. Can I rely on the CLR to be "smart enough" to never do this for the main UI thread (due to thread-affinity of the UI)? Then I could call GetCurrentThreadId to get the main UI-thread's unmanaged thread id for comparison.

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  • How do I wait for all other threads to finish their tasks?

    - by Mike
    I have several threads consuming tasks from a queue using something similar to the code below. The problem is that there is one type of task which cannot run while any other tasks are being processed. Here is what I have: while (true) // Threaded code { while (true) { lock(locker) { if (close_thread) return; task = GetNextTask(); // Get the next task from the queue } if (task != null) break; wh.WaitOne(); // Wait until a task is added to the queue } task.Run(); } And this is kind of what I need: while (true) { while (true) { lock(locker) { if (close_thread) return; if (disable_new_tasks) { task = null; } else { task = GetNextTask(); } } if (task != null) break; wh.WaitOne(); } if(!task.IsThreadSafe()) { // I would set this to false inside task.Run() at // the end of the non-thread safe task disable_new_tasks = true; Wait_for_all_threads_to_finish_their_current_tasks(); } task.Run(); } The problem is I don't know how to achive this without creating a mess.

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  • Repeated host lookups failing in urllib2

    - by reve_etrange
    I have code which issues many HTTP GET requests using Python's urllib2, in several threads, writing the responses into files (one per thread). During execution, it looks like many of the host lookups fail (causing a name or service unknown error, see appended error log for an example). Is this due to a flaky DNS service? Is it bad practice to rely on DNS caching, if the host name isn't changing? I.e. should a single lookup's result be passed into the urlopen? Exception in thread Thread-16: Traceback (most recent call last): File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner self.run() File "/home/da/local/bin/ThreadedDownloader.py", line 61, in run page = urllib2.urlopen(url) # get the page File "/usr/lib/python2.6/urllib2.py", line 126, in urlopen return _opener.open(url, data, timeout) File "/usr/lib/python2.6/urllib2.py", line 391, in open response = self._open(req, data) File "/usr/lib/python2.6/urllib2.py", line 409, in _open '_open', req) File "/usr/lib/python2.6/urllib2.py", line 369, in _call_chain result = func(*args) File "/usr/lib/python2.6/urllib2.py", line 1170, in http_open return self.do_open(httplib.HTTPConnection, req) File "/usr/lib/python2.6/urllib2.py", line 1145, in do_open raise URLError(err) URLError: <urlopen error [Errno -2] Name or service not known>

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  • Unload event for the default AppDomain?

    - by Zor
    Hi, I need to have an event fired whenever any AppDomain unloads - including the default one of the process. The problem with AppDomain.DomainUnload is that it only fires for non-default AppDomains. Furthermore, AppDomain.ProcessExit has limited execution time, which I cannot rely on. Any suggestions as to how I can achieve this would be greatly appreciated! (Alternatively, having an event fired when a background thread (Thread.IsBackground == True) works too.) Thanks in advance.

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  • how to emulate thread local storage at user space in C++ ?

    - by vprajan
    I am working on a mobile platform over Nucleus RTOS. It uses Nucleus Threading system but it doesn't have support for explicit thread local storage i.e, TlsAlloc, TlsSetValue, TlsGetValue, TlsFree APIs. The platform doesn't have user space pthreads as well. I found that __thread storage modifier is present in most of the C++ compilers. But i don't know how to make it work for my kind of usage. How does __thread keyword can be mapped with explicit thread local storage? I read many articles but nothing is so clear for giving me the following basic information will __thread variable different for each thread ? How to write to that and read from it ? does each thread has exactly one copy of the variable ? following is the pthread based implementation: pthread_key_t m_key; struct Data : Noncopyable { Data(T* value, void* owner) : value(value), owner(owner) {} int* value; }; inline ThreadSpecific() { int error = pthread_key_create(&m_key, destroy); if (error) CRASH(); } inline ~ThreadSpecific() { pthread_key_delete(m_key); // Does not invoke destructor functions. } inline T* get() { Data* data = static_cast<Data*>(pthread_getspecific(m_key)); return data ? data->value : 0; } inline void set(T* ptr) { ASSERT(!get()); pthread_setspecific(m_key, new Data(ptr, this)); } How to make the above code use __thread way to set & get specific value ? where/when does the create & delete happen? If this is not possible, how to write custom pthread_setspecific, pthread_getspecific kind of APIs. I tried using a C++ global map and index it uniquely for each thread and retrieved data from it. But it didn't work well.

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  • Why wait should always be in synchronized block

    - by diy
    Hi gents, We all know that in order to invoke Object.wait() , this call must be placed in synchronized block,otherwise,IllegalMonitorStateException is thrown.But what's the reason for making this restriction?I know that wait() releases the monitor, but why do we need to explicitly acquire the monitor by making particular block synchronized and then release the monitor by calling wait() ? What is the potential damage if it was possible to invoke wait() outside synch block, retaining it's semantics - suspending the caller thread ? Thanks in advance

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  • Java Thread - Synchronization issue

    - by Yatendra Goel
    From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

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  • Why is volatile not considered useful in multithreaded C or C++ programming?

    - by Michael E
    As demonstrated in this answer I recently posted, I seem to be confused about the utility (or lack thereof) of volatile in multi-threaded programming contexts. My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be volatile. Signal handlers, I/O registers, and variables modified by another thread all constitute such situations. So, if you have a global int foo, and foo is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus foo should be declared volatile (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution). How and where am I wrong?

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  • Using locks inside a loop

    - by Xaqron
    // Member Variable private readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile shared int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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  • How to end a thread in perl

    - by user1672190
    I am new to perl and i have a question about perl thread. I am trying to create a new thread to check if the running function is timed out, and my way of doing it is as below. Logic is 1.create a new thread 2.run the main function and see if it is timed out, if ture, kill it Sample code: $exit_tread = false; # a flag to make sure timeout thread will run my $thr_timeout = threads->new( \&timeout ); execute main function here; $exit_thread = true # set the flag to true to force thread ends $thr_timeout->join(); #wait for the timeout thread ends Code of timeout function sub timeout { $timeout = false; my $start_time = time(); while (!$exit_thread) { sleep(1); last if (main function is executed); if (time() - $start_time >= configured time ) { logmsg "process is killed as request timed out"; _kill_remote_process(); $timeout = true; last; } } } now the code is running as i expected, but i am just not very clear if the code $exit_thread = true works because there is a "last" at the end of while loop. Can anybody give me a answer? Thanks

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  • Failing faster when URL content is not found, howto

    - by Jam
    I have a thread pool that loops over a bunch of pages and checks to see if some string is there or not. If String is found, or not found response is near instant, however if server is offline or application is not running getting a rejection seems to take seconds How can I change my code to fail faster? for (Thread thread : pool) { thread.start(); } for (Thread thread : pool) { try { thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } } Here is my run method @Override public void run() { for (Box b : boxes) { try { connection = new URL(b.getUrl()).openConnection(); scanner = new Scanner(connection.getInputStream()); scanner.useDelimiter("\\Z"); content = scanner.next(); if (content.equals("YES")) { } else { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } catch (Exception ex) { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } }

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  • Java Thread execution on same data

    - by AR89
    first of all here is the code, you can just copy an paste import java.util.ArrayList; public class RepetionCounter implements Runnable{ private int x; private int y; private int[][] matrix; private int xCounter; private int yCounter; private ArrayList<Thread> threadArray; private int rowIndex; private boolean[] countCompleted; public RepetionCounter(int x, int y, int [][]matrix) { this.x = x; this.y = y; this.matrix = matrix; this.threadArray = new ArrayList<Thread>(matrix.length); this.rowIndex = 0; for(int i = 0; i < matrix.length; i++){ threadArray.add(new Thread(this)); } countCompleted = new boolean[matrix.length]; } public void start(){ for (int i = 0; i < threadArray.size(); i++){ threadArray.get(i).start(); this.rowIndex++; } } public void count(int rowIndex) { for(int i = 0; i < matrix[rowIndex].length; i++){ if (matrix[rowIndex][i] == x){ this.xCounter++; } else if (matrix[rowIndex][i] == y){ this.yCounter++; } } } @Override public void run() { count(this.rowIndex); countCompleted[this.rowIndex] = true; } public int getxCounter() { return xCounter; } public void setxCounter(int xCounter) { this.xCounter = xCounter; } public int getyCounter() { return yCounter; } public void setyCounter(int yCounter) { this.yCounter = yCounter; } public boolean[] getCountCompleted() { return countCompleted; } public void setCountCompleted(boolean[] countCompleted) { this.countCompleted = countCompleted; } public static void main(String args[]){ int[][] matrix = {{0,2,1}, {2,3,4}, {3,2,0}}; RepetionCounter rc = new RepetionCounter(0, 2, matrix); rc.start(); boolean ready = false; while(!ready){ for(int i = 0; i < matrix.length; i++){ if (rc.getCountCompleted()[i]){ ready = true; } else { ready = false; } } } if (rc.getxCounter() > rc.getyCounter()){ System.out.println("Thre are more x than y"); } else {System.out.println("There are:"+rc.getxCounter()+" x and:"+rc.getyCounter()+" y"); } } } What I want this code to do: I give to the object a matrix and tow numbers, and I want to know how much times these two numbers occurs in the matrix. I create as many thread as the number of rows of the matrix (that' why there is that ArrayList), so in this object I have k threads (supposing k is the number of rows), each of them count the occurrences of the two numbers. The problem is: if I run it for the first time everything work, but if I try to execute it another time I get and IndexOutOfBoundException, or a bad count of the occurrences, the odd thing is that if I get the error, and modify the code, after that it will works again just for once. Can you explain to me why is this happening?

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  • Multi-threading concept and lock in c#

    - by Neeraj
    I read about lock, though not understood nothing at all. My question is why do we use a un-used object and lock that and how this makes something thread-safe or how this helps in multi-threading ? Isn't there other way to make thread-safe code. public class test { private object Lock { get; set; } ... lock (this.Lock) { ... } ... } Sorry is my question is very stupid, but i don't understand, although i've used it many times.

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